Process for preparing in situ reticulated polyurethane foam

ABSTRACT

An improved process for in situ production of a reticulated, open-cell polyurethane foam which comprises reacting a polyester/polyether polyol mixture with an aromatic polyisocyanate having a ratio of isocyanate moieties to aromatic moieties of about 2:1 in the presence of a catalyst and a blowing agent, 
     the improvement comprises: 
     said polyol mixture being 
     (a) 80 to 95 parts by weight of polyester polyol and 
     (b) 20 to 5 parts by weight of polyoxypropylene polyether polyol or a mixed poly(oxyethylene/oxypropylene polyether polyol, each having at least one polymer of ethylenically unsaturated monomers dispersed therein and a stabilizing surfactant for polyether polyurethane foam, 
     and said process produces a polyurethane foam which has excellent strength properties and an exceeding low resistance to air flow.

The present invention relates to production of polyurethane foam whichhas a low resistance to air flowing therethrough due to its highly openstructure.

BACKGROUND OF THE INVENTION

Cellular solid polymers, often referred to as "foams" can be prepared bygenerating a gas during the polymerization of the liquid reactionmixture. The gas generated causes foaming of the reaction material whichis normally in a plastic or liquid state. The polymerization reactioncontinues while the foaming occurs until the polymer sets or gels intothe cellular pattern formed by the foam bubbles. The solidified polymerthus becomes a cellular solid mass popularly known as a "foam".Polyurethane foams are generally prepared by the reaction of an activehydrogen-containing compound and a polyisocyanate, in the presence of ablowing agent such as water, and usually, a reaction catalyst and foamstabilizer.

Polyurethane foam is used widely as a flexible cellular product in thecomfort cushion market (furniture, bedding, automotive); in the textilearea (apparel, blankets); in the industrial packaging and insulatingfields; in other household furnishings and sponges; filters, and thelike. The versatility of polyurethane foam, permitting its use indiverse markets, results in substantial part from the nature and varietyof the raw materials which are used to produce the foam products, aswell as the manner in which the raw materials and the resultant foam areprocessed. Foams ranging widely in density and hardness, in tensile andtear properties, in resistance to compression set and fatigue, inresilience and hysteresis, in durability and toughness are obtained byselection and variation in raw materials and processing conditions. Animportant further characteristic in foam that likewise varies widely isits breathability, or resistance to air flow, of the basic cellularstructure.

The cellular solid polymer foam has a skeletal framework of relativelyheavy strands forming an outline for the cell structure. The strands ofthe skeletal framework are conventionally connected by very thinmembranes, or windows, which form the walls of the cells. In open-celledfoams, some of the windows are open or torn in each cell thus forming aninterconnecting network open to air flow. However, conventionalpolyurethane foams are not sufficiently porous or open-celled to exhibitvery low resistance to air flow therethrough which are required for manyutilities, such as filtering. Accordingly, in attempting to improve theproperties of such open-celled foams in a desired direction, the art hastried various post-forming methods of reticulating, or increasing thedegree of openness, by breaking or removing the residual cell windows ofsuch foams. Chemical, mechanical and thermal reticulation means have allbeen used.

For example, removing cell walls has been suggested by using thehydrolyzing action of water in the presence of an alkali metalhydroxide. By carefully adjusting the conditions during the hydrolysisreaction, it has been demonstrated that cell windows can be removedwithout adversely affecting the skeletal framework. Reticulation canalso be carried out by melting the windows by, for example, a hightemperature flame front to heat the cell windows or walls to above themelting point of the polymer. Thus, it was proposed that by carefullyregulating the conditions under which this process is carried out, thecell windows can be melted without adversely affecting or melting theskeletal strands.

Various purely mechanical means to reticulate both flexible and rigidfoams have also been suggested. For example, the art has utilized aprocedure of compressing, mangling or wringing a flexible foam to openthe pores to render it more useful as a sound insulating or soundabsorbing medium. Foams have been made more open, to improve soundabsorbing properties, by heating with super-heated steam at 140° C., orby blowing with compressed air or high velocity liquids.

Whatever post treatment is used, it must of necessity produce someeffect upon the stalk or skeletal structure of the foam regardless ofhow minimal such effect is. In many cases, when working with a pigmentedfoam, the color intensity and hue are substantially changed by thepost-polymerization reticulation treatment. This can result in somedifficulty in color matching for certain applications. Moreover,post-treatment methods add significantly to the cost of the foam.Therefore, a method for producing a substantially open-cellednonlustrous foam in situ during the reaction or foaming process, withoutthe necessity of an additional post polymerization treatment step, haslong been sought and would be an advance in the art.

The art has been at least partially successful in obtaining open-celledpolyether type polyurethane wherein the polyurethane is prepared using apolyhydric polyether as the active hydrogen-containing reactant. Forexample, in U.S. Pat. No. 3,433,752, an open-celled, rigid, polyetherpolyurethane foam is produced by the addition of an alkali metal salt ofa sulfonated high molecular weight fatty acid. In Canadian Pat. No.797,893, the preparation of a polyalkylene ether polyurethane having anopen structure is disclosed which includes the addition of a petroleumhydrocarbon liquid, e.g., kerosene or mineral oil, as a cell openingagent which causes the cell membranes of the foam to rupture during thefoaming process, thus allegedly providing an open material. The intentof this process is to prevent shrinking of the foam during cooling whichoften occurs with a substantially fully closed cell structure. However,the above process is explicitly limited to polyalkylene etherpolyurethane and does not result in a completely open structure, butmerely one in which sufficient membranes are removed to permit at leastsome air permeability throughout the internal foam structure. Also seeU.S. Pat. No. 3,454,504.

In Canadian Pat. No. 797,892, an open-celled polyether polyurethane foammaterial is obtained by the reaction of a polyhydric polyether compoundwith an organic polyisocyanate and blowing agent in the presence of aninert organic liquid solvent such as methylene chloride, acetone, hexaneor pentane.

U.S. Pat. No. 3,178,300 describes a process for preparing "skeletal"polyurethane foam by mixing an organic polyisocyanate with castor oil inthe presence of an alkyl silane oxyalkylene block copolymer (asurfactant), a blowing agent and a monohydric organic compound, such asa monohydric alcohol or monocarboxylic acid. This material has a limitedusefulness, however, because of the low structural strength caused bythe chain-stopping monohydric additive, which limits its strength, andthe relatively coarse cell structure. Further, castor oil is notoriouslydifficult to use as a sole polyhydroxy reactant. The reaction withcastor oil is highly exothermic, often causing scorching or even burningof the foam, and often the formation of odoriferous by-products.

U.S. Pat. No. 3,165,483 describes a process for making a skeletal foamby reacting a polyisocyanate with either castor oil or a polyhydricpolyether in the presence of a silane-oxyalkylene block copolymer and ofan unreactive hydrocarbon or halohydrocarbon, ester, aldehyde and/orketone. These materials are also indicated to be useful as filters.

U.S. Pat. No. 3,748,288 describes production of an open polyester-typeurethane foam by the addition of a minor proportion of a polyetherpolyol reagent and a small amount of a hydrophobic, anti-foamingorgano-silicone compound. U.S. Pat. No. 3,884,848 describes thereplacement of the hydrophobic, anti-foaming organo-silicone compoundwith at least one ester of the formula (RCOO)_(n) R', wherein R and R'are alkyl or alkenyl groups having from one (1) thirty (30) carbonatoms, at least three carbon atoms, and n is an integer from one (1) tothree (3).

BRIEF DESCRIPTION OF THE INVENTION

It has now been discovered that an extremely stable highly reticulated,open-celled polyester-type polyurethane foam with excellent physicalproperties can be directly produced, in-situ, from conventional foammaking formulations if about 5 to 20% by weight of the polyester polyolreactant is replaced by a modified polyether polyol. In the context ofthe present invention, a "modified" polyether polyol means a polyetherpolyol having dispersed therein either polymers of ethylenicallyunsaturated monomers such as polyacrylonitrile, polystyrene, andpoly(styrene coacrylonitrile), or polyurea.

In addition to negating the need for a small amount of hydrophobic,anti-foaming organo-silicone compound or an ester of the formula(RCOO)_(n) R' as described above, this discovery yields an in situopen-celled polyester polyurethane foam with much better physicalproperties than the aforementioned art.

Accordingly, it is a primary object of the present invention to producea flexible polyurethane foam having very low resistance to air flowwhich can be produced in situ.

It is another object of the present invention to produce foam having theadvantageous characteristics of a reticulated structure withoutsacrificing the strength of the skeletal structure of the foam.

It is still another object of this invention to provide selection of rawmaterials which will produce strong, resilient, highly breathable foamproducts free of defects caused by prior art reticulating means andwhich can be processed on conventional foam processing equipment.

The aforesaid and other objects of the present invention will becomefully apparent from the following description.

DETAILED DESCRIPTION

Conventionally, flexible polyester polyurethane foams are produced byreacting a polyisocyanate with a polyester polyol in the presence ofwater which reacts to form a gaseous blowing agent. By replacing a smallamount of the polyester polyol reactant with a modified polyetherpolyol, an extremely stable highly reticulated foam can be produced insitu and troublesome additives can be avoided. An amount 5 to 20% byweight of the polyester polyol can be replaced by the modified polyetherpolyol. Use of more than 20% by weight, based on total polyol, ofmodified polyether polyol results in a foam which has a high resistanceto air flow and is considered to be not reticulated. With amounts up to5% of modified polyether polyol an unstable system is produced and thefoam collapses before curing. An amount of from about 8 to 15% by weightof modified polyether polyol, based on total polyol, is preferred andabout 10% is most preferred.

Thus this invention concerns an improved process for in situ productionof a reticulated, open-cell polyurethane foam which comprises reacting apolyester/polyether polyol mixture with an aromatic polyisocyanatehaving a ratio of isocyanate moieties to aromatic moieties of about 2:1in the presence of a catalyst and a blowing agent,

the improvement comprises:

said polyol mixture being

(a) 80 to 95 parts by weight of polyester polyol and

(b) 20 to 5 parts by weight of

(i) polyoxypropylene polyether glycol or

(ii) a mixed poly(oxyethylene/oxypropylene) polyether polyol,

into which is dispersed polymers of polyurea or ethylenicallyunsaturated monomers, such as polyacrylonitrile, polystyrene, orpoly(styrene coacrylonitrile)or.

Modified polyether polyols are typically poly(oxyethylene/oxypropylene)ether polyols into which is dispersed poly(styrene coacrylonitrile), orpolyurea. Modified polyether polyols are commercially available fromseveral companies, including Union Carbide (supplied as "PolymerPolyol"), BASF (supplied as "Graft Polyol"), Dow (supplied as"Co-polymer Polyol"), and Mobay (supplied as PHD Polyol). Union Carbide,BASF, and Dow use the poly(styrene coacrylonitrile) system, whereasMobay uses the polyurea system. Some examples of commercially availablemodified polyether polyols are as follows:

                  TABLE I                                                         ______________________________________                                        POLYETHER POLYOL       TYPE                                                   ______________________________________                                        Union Carbide          E488                                                   "Polymer Polyols"      E547                                                                          E464                                                                          E543                                                                          E363                                                                          E579                                                   BASF                   P994LV                                                 "Graft Polyols"                                                               Dow                    XAS-10946                                              "Copolymer Polyols"    XAS-10963                                              Mobay                  E9232                                                  "PHD Polyols"                                                                 ______________________________________                                    

Some modified polyether polyols can be prepared by the proceduredescribed by Critchfield et al, Rubber Chemistry and Technology, Vol.45, No. 5, pp. 1467-1477 (1972) and U.S. Pat. No. Re. 23,817. Apolyether polyol (e.g., polyoxypropylene polyol) is reacted with styreneand acrylonitrile in the presence of a free radical catalyst and theresulting modified polyether polyol is isolated.

The polyester polyol used in this invention is selected fromconventional polyester polyols known to those skilled in the art to besuitable in polyurethane foam production. The polyester polyol reactantusually has a molecular weight of at least about 400 and optimallybetween about 500 and about 5000 as determined by molecular weightaverage. The hydroxyl number of the compound is correspondingly in therange of from about 15 to about 300. Generally a polyester having amolecular weight average of about 3000 and a hydroxyl functionality of 2to 3 is preferred. The polyesters are obtained by esterification ofpolycarboxylic acids (or their acid halides or anhydrides) withpolyhydric alcohols.

The preferred acids are the dicarboxylic acids containing from about 4to about 12 carbon atoms in the molecule. Examples of such preferredcarboxylic acid compounds which can be used include, for example,aromatic acids such as phthalic acid, terephthalic acid, isophthalicacid, tetrachlorophthalic acid, cycloaliphatic acids such as dimerizedlinoleic acid, maleated and fumarated rosin acids andcyclohexane-1,4-diacetic acid, but especially the aliphatic acids suchas tricarballylic, oxydipropionic, succinic, glutaric, adipic, azelaic,suberic, sebacic acids, or combinations of such acids. The polyesterpolyols can also be prepared from corresponding lactones, such asgamma-butyrolactone or epsilon-caprolactones, for example.

The polyhydric alcohol used in the preparation of this polyester polyolis generally a mixture of a dihydric and a trihydric, or polyhydricalcohol of high hydroxyl value. Preferably, a mixture of polyols, themajor portion having a functionality of two and the minor portion havinga functionality of three is used. This mixture of di- and tri-functionalpolyols is utilized to give an average functionality of between two andthree. A functionality of greater than two is desirable to providecross-linking in the reaction between the polyester polyol and thepolyisocyanate to form a flexible, but strong foam. It has been found tobe preferable to obtain this additional functionality by using trihydricor higher polyols in a minor amount when forming the polyester polyol.

For preparing flexible foams, the polyols most preferably include theglycols, such as neopentyl glycol, ethylene glycol, diethylene glycol,hexamethylene glycol, 1,4- and 1,3-butylene glycol, 1,3- and1,2-propylene glycol and the corresponding dipropylene glycols. The mostuseful monomeric triols include the aliphatic triols, such astrimethylolethane, trimethylolpropane, 1,2,4-butanetriol,1,2,6-hexanetriol, glycerol, and triethanolamine. Aromatic polyols canalso be used, such as trihydroxymethyl benzene and a functionality closeto 3.

The most preferred polyester polyol reactant is diethylene glycoladipate polyester polyol having a molecular weight of about 3000.

The polyisocyanate used in this invention is likewise a conventionalmaterial used in producing polyurethane foam. Preferably, thepolyisocyanate is toluene diisocyanate (TDI). However, otherpolyisocyanates having a ratio of isocyanate groups to aromatic rings ofabout 2:1 are suitable and include phenylene diisocyanate, naphthalenediisocyanate, diphenyl-4,4'-diisocyanate and xylene diisocyanate.

In addition to the polyol mixture of this invention conventional blowingagents and catalysts are employed to produce the polyurethane foam.Water and/or readily volatile organic substances are used as blowingagents in the process according to the invention. The blowing agent isemployed in an amount from about 1 to about 15 parts by weight per 100parts by weight of total polyol reactant, the particular blowing agentand amount thereof depending upon the type of foam product desired.Flexible foam formulations usually contain up to about six pphp ofwater. The selection and amount of blowing agent in any particular foamformulation is well within the skill of the cellular polyurethane art.Suitable organic blowing agents are acetone, ethyl acetate, halogenatedalkanes, such as methylene chloride, chloroform, ethylidene chloride,vinylidene chloride, monofluorotrichloromethane, chlorofluoromethane ordichlorodifluoromethane, butane, hexane, heptane or diethyl ether. Ablowing effect can also be obtained by adding compounds which decomposeat temperatures above room temperature to liberate gases, for example,azo compounds such as azoisobutyric acid nitrile which liberatenitrogen.

Catalysts and surfactants are also frequently used in the processaccording to the invention. Conventional catalyst/surfactant systemsdiffer depending on whether a polyester polyol or a polyether polyol isused to produce foam. It is a significant part of the present inventionthat a conventional polyether polyol-type catalyst/surfactant system isused, even required. It has been discovered that in the process of thisinvention a polyester polyol-type catalyst/surfactant system cannot beused because the foam is unstable and collapses even though the majorityof polyol is polyester polyol. It was unexpectedly discovered that apolyether polyol-type catalyst/surfactant system produced quitedifferent results. The catalysts used are known and include tertiaryamines such as triethylamine, tributylamine, N-methyl-morpholine,N-ethyl-morpholine-N-ocomorpholine,N,N,N',N'-tetramethylethylenediamine, 1,4-diaza-bicyclo-(2,2,2)-octane,N-methyl-N'-dimethylaminoethyl-piperazine, N,N-dimethyl benzylamine,bis-(N,N-diethylaminoethyl)-adipate, N,N-diethylbenzylamine, pentamethyldiethylenetriamine, N,N-dimethylcyclohexylamine,N,N,N',N'-dimethyl-phenylethylamine, 1,2-dimethylimidazole and2-methylimidazole, triethylene diamine, bis(2-dimethylamino ethyl)ether.

The tertiary amines which contain hydrogen atoms capable of reactingwith isocyanate groups include triethanolamine, triisopropanolamine,N-methyldiethanolamine, N-ethyldiethanolamine, N,N-dimethylethanolamineor their reactions products with alkylene oxides such as propylene oxideand/or ethylene oxide, 2,2,4-trimethyl-2-silamorpholine or1,3-diethylaminomethyl-tetramethyl-disiloxane.

The catalysts used may also be bases which contain nitrogen such astetraalkyl ammonium hydroxides or alkali metal hydroxides such as sodiumhydroxide, alkali metal phenolates such as sodium phenolate or alkalimetal alcoholates such as sodium methylene. Hexahydrotriazines may alsobe used as catalysts.

Organic metal compounds may also be used as catalysts according to theinvention, especially organic tin compounds, which are the preferredcatalysts.

Organic tin compounds used are preferably tin (II) salts of carboxylicacids such as tin (II)-acetate, tin (II) octoate, tin (II)-ethylhexoacteand tin (II)-laurate and the dialkyl tin salts of carboxylic acids suchas dibutyl tin diacetate, dibutyl tin dilaurate, dibutyl tin maleate ordioctyl tin diacetate.

The catalyst is generally added in amounts of from about 0.05 to about 2weight percent and preferably from about 0.1 to about 1 weight percent,based on the total weight of the active hydrogen-containing compoundspresent in the reaction, i.e., the polyester polyol and the polyetherpolyol.

It is conventional wisdom in the art, to utilize a foam-stabilizingemulsifier-surfactant and foaming agent in balanced proportions toobtain a foam of a desired cell size, structure and density. Generally,the emulsifier-surfactant is balanced with the amounts of catalyst andwater to obtain the desired foam.

The foam-stabilizing emulsifiers used in the present invention arepolymeric organo-silicon compounds which are partially hydrophilic andcompatible with at least one of the polyols. Such organo siliconsurfactant-emulsifiers are well known to the art, described extensivelyin the published literature, and sold commercially. The commerciallyavailable organo silicon surfactant-emulsifiers are generally sold withspecific instructions as to their suitability for polyether polyol-typeurethane foam production. As noted above, a surfactant-emulsifiersuitable for one polyol type is not suitable for use in a foamingreaction based on the other type. Further, these surfactant-emulsifiersare proprietary products, sold without disclosure as to their precisechemical structure. However, the surfactant-emulsifiers used forpolyether polyol-containing reaction mixtures are known to depress thesurface tension to a greater extent than do the organo siliconsurfactants used with polyester polyols.

In the process of the present invention, however, where the urethanefoam is prepared from a reaction mixture containing as the major portionof the polyol reagent a polyester polyol, it is surprising that thesurfactant-emulsifiers which are most effective, are the typecommercially used with polyether polyols.

The most generally available organo silicon emulsifier surfactants arepolymers which contain a plurality of silicon atoms (which form part ofthe hydrophobic portion of the polymer molecule) and a long chainhydrophilic group, for example, including a polyoxyalkylene ether group.In the more common organo silicon emulsifier surfactant compounds, thesilicon is present as a siloxane group, i.e., --Si--O. These compoundsare described in detail in U.S. Pat. No. 3,884,848 which description ishereby incorporated by reference.

Although foaming of the present resin reactant is effected simply, it isalso possible to add, although not necessary, supplemental foamingmaterials or functional additives, e.g., fillers, absorbants,antioxidants, enzymes, dyes, fire retardants, pigments, biocides, andthe like, such as those well known to the artificial sponge foaming art.The additives can either be inert and thus physically held in the foamstructure, or chemically reactive with reactive species in the resinreactant in which case the additive may be bound chemically into thefoam product.

Production of foam by the process of this invention can be achieved byuse of a conventional foam making machine operated in the mannercurrently known to those skilled in the art. Reactants and additives aremixed together and allowed to rise and react freely on a moving castingconveyor in the known manner, and then cured to produce large slabs of areticulated foam having low resistance to fluid (e.g., air) flow.

The following examples will aid in explaining, but should not be deemedas limiting, practice of the present invention. In all cases, unlessotherwise noted, all parts and percentages are by weight.

EXAMPLE 1

A polyol mixture is prepared from 90 parts of a diethylene glycoladipate polyester polyol having a molecular weight of 3000 and 10 partsof a modified polyether polyol sold by Union Carbide Corporation underthe name Niax E488, which is a polymer polyol. That polyol mixture (100parts) is reacted with toluene diisocyanate (52 parts), water (4 parts),organotin catalyst (0.8 parts), amine catalyst (0.9 parts), and asilicone surfactant (1.0 parts) under foaming conditions wherein thecream time is 12 seconds, the rise time is 105 seconds with a strong gelstrength. The catalysts are stannous octoate (in dioctyl phthalate in aratio of 1:2) and C124 (Niax A-1, a proprietary tertiary amine productof Union Carbide, in dipropylene glycol in a ratio of 1:6). The siliconesurfactant is L6202, a poly(siloxane)/poly(ether) co-polymer from UnionCarbide. The product is a highly reticulated polyurethane foam.

EXAMPLE 2 (Comparison)

As a comparison, the procedure of Example 1 is repeated except that thepolyol reactant contains no polyether polyol and is all polyesterpolyol, and the catalysts and surfactant systems are those typicallyused for polyester foam. During the foaming, a cream time of 9 secondsand a rise time of 64 seconds are noted with only a weak to moderate gelstrength. The following Table II presents the properties of the foams ofExample 1 and 2.

                  TABLE II                                                        ______________________________________                                                                       Ex. 2                                                         Ex. 1  Ex. 2    Thermally                                                     As-Made                                                                              As-Made  Reticulated                                    ______________________________________                                        Density (lbs./ft.sup.3)                                                                        1.77     1.80     1.68                                       Air Permeability (ft.sup.3 /min/ft.sup.2)                                                      501.0    6.2      365.0                                      Tensile Strength (lbs/in.sup.2)                                                                15.6     18.2     21.9                                       Elongation (%)   158.0    115.0    197.0                                      Tear Strength (lbs/in)                                                                         2.8      2.8      3.6                                        CLD (lbs/in.sup.2)-25%                                                                         0.45     0.69     0.50                                       ______________________________________                                    

EXAMPLE 3

To study the effects of the amount of modified polyether polyol on foamcharacteristics, Example 1 is repeated using 5 parts, 15 parts and 20parts of Niax E488 in place of the 10 parts of Example 1. Properties ofthe resulting foam are summarized in Table III below.

                                      TABLE III                                   __________________________________________________________________________    Parts polyether                                                               polyol per 100                                                                parts total polyol                                                                     DEN AIR PERM.                                                                            PPI*                                                                              CLD.sub.25                                                                        TEN.                                                                              EL.                                                                              TEAR                                       __________________________________________________________________________     5       2.27                                                                              410    15  0.60                                                                              12.6                                                                               91                                                                              2.2                                        10       1.77                                                                              501    65  0.45                                                                              15.6                                                                              158                                                                              2.8                                        15       1.58                                                                              415    65  0.36                                                                              15.9                                                                              173                                                                              2.9                                        20       1.58                                                                              228    70  0.45                                                                              21.3                                                                              253                                                                              4.2                                        __________________________________________________________________________     *PPI means visual pores per lineal inch.                                 

EXAMPLES 4-12

Example 1 is repeated using the following polyether polyols in place ofthe specific one in Example 1. Example 4 is a comparison with aconventional polyether polyol, while Examples 5-12 are modifiedpolyether polyols used according to the present invention. Airpermeability of the foam of each example is shown.

    ______________________________________                                        Example       Polyether polyol                                                                           Air perm.                                          ______________________________________                                         4 (comparison)                                                                             CB           133                                                 5            XB           380                                                 6            XC           448                                                 7            XD           340                                                 8            XE           425                                                 9            XF           463                                                10            XG           518                                                11            XH           534                                                12            XI           542                                                ______________________________________                                    

Polyether polyol CB (Example 4) is a conventionalpoly(oxyethylene/oxypropylene) ether polyol.

Polyether polyol XB is BASF P994 LV Graft Polyol, which is a modifiedpolyether polyol based on a poly(styrene coacrylonitrile) system.

Polyether polyols XC, XD, XF and XI are respectively Union Carbide'sNiax E464, E543, E363 and E579 Polymer Polyols, which are modifiedpolyether polyols based on a poly(styrene coacrylonitrile) system.

Polyether polyols XE and XG are respectively Dow XAS-10946 and XAS-10963Copolymer Polyols, which are modified polyether polyols based on apoly(styrene coacrylonitrile) system.

Polyether polyol XH is Mobay E9232 PHD polyol, which is a modifiedpolyether polyol based on a polyurea system.

It is understood that the foregoing detailed description is given merelyby way of illustration and that many variations may be made thereinwithout departing from the spirit of this invention.

What is claimed is:
 1. In an improved process for in situ production of a reticulated open-cell polyurethane foam which comprises reacting a polyester/polyether polyol mixture with an aromatic polyisocyanate having a ratio of isocyanate moieties to aromatic moieties of about 2:1 in the presence of a catalyst and a blowing agent,the improvement comprises: said polyol mixture being (a) 80 to 95 parts by weight of the mixture of a polyester polyol and (b) 20 to 5 parts by weight of polyoxypropylene polyether polyol or a mixed poly(oxyethylene/oxypropylene) polyether polyol, having at least one of a polyurea or a polymer of ethylenically unsaturated monomers dispersed therein and a stabilizing surfactant for polyether polyurethane foam.
 2. The process according to claim 1 wherein the polyisocyanate is toluene diisocyanate.
 3. The process according to claim 1 wherein the polyether polyol (b) amounts to about 10 parts by weight of the polyol mixture.
 4. The process according to claim 1 wherein the polyether polyol is a polyoxypropylene polyether polyol into which is dispersed poly(styrene coacrylonitrile).
 5. The process according to claim 1 wherein the polyether polyol is a poly(oxyethylene/oxypropylene) polyether polyol into which is dispersed poly(styrene coacrylonitrile).
 6. The process according to claim 1 wherein the polyether polyol is a poly(oxyethylene/oxypropylene) polyether polyol into which is dispersed polyurea.
 7. The process according to claim 1 wherein the polyether polyol is a poly(oxypropylene) polyether polyol into which is dispersed polyurea.
 8. In an improved process for in situ production of a reticulated open-cell polyurethane foam which comprises reacting a polyester/polyether polyol mixture with an aromatic polyisocyanate having a ratio of isocyanate moieties to aromatic moieties of about 2:1 in the presence of a catalyst and a blowing agent,the improvement comprises: said polyol mixture being (a) 80 to 95 parts by weight of the mixture of a polyester polyol and (b) 20 to 5 parts by weight of polyoxypropylene polyether polyol or a mixed poly(oxyethylene/oxypropylene) polyether polyol, having at least one of polystyrene, polyacrylonitrile, polyurea or poly(styrene coacrylonitrile) dispersed therein and a stabilizing surfactant for polyether polyurethane foam.
 9. The process according to claim 8 wherein the polyisocyanate is toluene diisocyanate.
 10. The process according to claim 8 wherein the polyether polyol (b) amounts to about 10 parts by weight of the polyol mixture.
 11. The process according to claim 8 wherein the polyether polyol is a polyoxypropylene polyether polyol into which is dispersed poly(styrene coacrylonitrile).
 12. The process according to claim 8 wherein the polyether polyol is a poly(oxyethylene/oxypropylene) polyether polyol into which is dispersed poly(styrene coacrylonitrile).
 13. The process according to claim 8 wherein the polyether polyol is a poly(oxyethylene/oxypropylene) polyether polyol into which is dispersed polyurea.
 14. The process according to claim 8 wherein the polyether polyol is a poly(oxypropylene) polyether glycol into which is dispersed polyurea. 